Hey there! I'm happy to help!
First, we'll want to find the vertex of this parabola.
Given the equation y=ax^2+bx+c, the formula for the x-coordinate of the vertex is always
.
In our equation here, our a is 1 and our b is -2.
Now that we have our x-value of our vertex, we can plug it into our equation to find our y-coordinate.
y=1²-2(1)-5
y=1-2+5
y=-1+5
y=4
So, our vertex is at (1,4).
Vertex form is y=a(x-h)²+ k where (h,k) is our vertex. We know now that our vertex is (1,4) and we also know that our a is 1, so we can simply plug it in to this equation.
y=(x-1)²+4
Have a wonderful day and keep on learning! :D